This relates generally to integrated circuits, and more particularly, to integrated circuits with decoupling capacitors.
Decoupling capacitors are often used to help provide more stable power supply voltages to circuitry on integrated circuits. Decoupling capacitors shunt high frequency noise on direct current (DC) power supply lines to ground power supply lines, thereby preventing the noise from reaching powered circuit components. In a scenario in which a power supply is required to switch between various modes of operation, an adequate decoupling capacitance can act as an energy reserve that lessens the magnitude of undesired dips in power supply voltage during mode switching events.
Advances in integrated circuit design require power supplies to supply stable power for integrated circuits operating at high data rates and clock speeds. This requires increasing amounts of decoupling capacitance per unit integrated circuit area. A large decoupling capacitance could occupy a disproportionate amount of valuable surface area on an integrated circuit.
In order to satisfy strict polysilicon density requirements for modern processes, each decoupling capacitor includes dummy polysilicon structures in close proximity to its polysilicon gate. The polysilicon gate is connected to a power supply line, whereas the dummy polysilicon structures are electrically disconnected from operational circuitry (i.e., the dummy polysilicon structures are not actively driven to any specific voltage level). Integrated circuits that include multiple decoupling capacitor array blocks formed in this arrangement may have a significant portion of available die space occupied by decoupling capacitor circuitry.